1. Field of the Invention
This invention relates generally to continuous casting molds and, more particularly, to an adjustable width continuous casting mold having narrow-side plates arranged between broadside plates that are held by clamping forces.
2. Description of the Related Art
Molds of the type heretofore used in the continuous casting of molten metal slabs are described and illustrated in numerous prior art patents such as U.S. Pat. Nos. 3,964,727 of Jun. 22, 1976, and 4,124,058 of Nov. 7, 1978. See also EP 0 107 564 A1, DE 27 02 976 C2, DE 38 38 010 A1, and DE 36 40 096 C1. Typically, continuous casting molds comprise a pair of opposed, spaced apart side walls which are adjustably clamped between opposed, spaced apart front and rear walls. The four walls are configured as a box-like container or frame having open upper and lower ends to form a casting cavity interiorly of the walls. Molten metal is poured into the open upper end of the mold and is partially cooled within the cavity as the metal flows downwardly through the cavity under the influence of gravity so as to form a solidified skin surrounding an interior core of molten metal. This skin and core together form a continuous elongated extrusion-like slab which emerges from the open lower end of the mold and is thereafter cooled to form a solid slab.
As described in the aforementioned U.S. Pat. No. 3,964,727, the mold side walls (often referred to as side wall members) are supported upon mounting blocks so that they may be adjusted inwardly toward each other or outwardly away from each other by adjusting longitudinal movement of support shafts carried by the blocks. The mounting blocks also are provided with bolts to support the blocks to the front and rear walls of the mold, and plungers or separators to separate the mold walls against a spring pressure to thus loosen the side wall members for adjustment when desired. Thus, during adjustment of the widths of the conventional molds as described above, the front and rear walls of the mold are held sufficiently apart to unclamp the side wall members so that the side wall members may be adjusted inwardly or outwardly to change the width of the metal slab.
One disadvantage associated with the prior art configurations described above, however, is that when the narrow-side plates are adjusted to a determined slab width and, at a given casting speed, to a determined conicity or amount of taper, unforeseeable thermal changes in the length of the broadside plates may occur as a result of fluctuations in the production sequence. These thermal changes may, for example, include a change in the melt temperature or a change in the cooling conditions in the mold.
The effects of thermal changes is particularly pronounced at the beginning of casting, that is, when filling the mold, since the temperatures occurring in the upper mold region are higher than those at the mold output because of the higher thermal loading. Since the broadside plates and narrow-side plates are arranged within a rigid mold frame, the thermal change in the length of the broadside plates leads to a displacement of the narrow-side plates so that the adjusted amount of taper of the narrow-side plates is changed. If the forces brought about by the thermal change in length exceed the contact pressure forces, the displacement of the narrow-side plates in proportion to the broadside plates can result in wear at the copper plates of the broadside plates. In any event, the results will be undesirable for continuous casting.
It has been proposed to counteract the problem of thermal changes in nonadjustable width molds by arranging inserts between the broadside plates and the edge regions of the contacting narrow-side plates, which inserts extend over the height of the mold. For an illustrative example of such a configuration, reference may be made to Published Specification DAS 19 39 777. Heretofore, however, it has not been possible to account for thermal changes in an adjustable width mold whereby the amount of taper of the narrow-side plates, once adjusted, is maintained during casting.
It is therefore an object of the present invention to provide an adjustable width continuous casting mold which avoids the disadvantages described above and in which the amount of taper of the narrow-side plates, once adjusted, is maintained during casting even under altered operating conditions and which prevents damage to the broadside plates.